tools/dasm/src/java_cup/terminal.java

package java_cup;
 
import java.util.Enumeration;
import java.util.Hashtable;

/** This class represents a terminal symbol in the grammar.  Each terminal 
 *  has a textual name, an index, and a string which indicates the type of 
 *  object it will be implemented with at runtime (i.e. the class of object 
 *  that will be returned by the scanner and pushed on the parse stack to 
 *  represent it). 
 *
 * @version last updated: 11/25/95
 * @author  Scott Hudson
 */
public class terminal extends symbol {

  /*-----------------------------------------------------------*/
  /*--- Constructor(s) ----------------------------------------*/
  /*-----------------------------------------------------------*/

  /** Full constructor.
   * @param nm the name of the terminal.
   * @param tp the type of the terminal.
   */
  public terminal(String nm, String tp) 
    {
      /* superclass does most of the work */
      super(nm, tp);

      /* add to set of all terminals and check for duplicates */
      Object conflict = _all.put(nm,this);
      if (conflict != null)
    // can't throw an execption here because this is used in static 
    // initializers, so we do a crash instead
    // was:
    // throw new internal_error("Duplicate terminal (" + nm + ") created");
    (new internal_error("Duplicate terminal (" + nm + ") created")).crash();

      /* assign a unique index */
      _index = next_index++;

      /* add to by_index set */
      _all_by_index.put(new Integer(_index), this);
    }

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

  /** Constructor with default type. 
   * @param nm the name of the terminal.
   */
  public terminal(String nm) 
    {
      this(nm, null);
    }

  /*-----------------------------------------------------------*/
  /*--- (Access to) Static (Class) Variables ------------------*/
  /*-----------------------------------------------------------*/

  /** Table of all terminals.  Elements are stored using name strings as 
   *  the key 
   */
  protected static Hashtable _all = new Hashtable();

  /** Access to all terminals. */
  public static Enumeration all() {return _all.elements();};

  /** Lookup a terminal by name string. */ 
  public static terminal find(String with_name)
    {
      if (with_name == null)
    return null;
      else 
    return (terminal)_all.get(with_name);
    }

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

  /** Table of all terminals indexed by their index number. */
  protected static Hashtable _all_by_index = new Hashtable();

  /** Lookup a terminal by index. */
  public static terminal find(int indx)
    {
      Integer the_indx = new Integer(indx);

      return (terminal)_all_by_index.get(the_indx);
    }

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

  /** Total number of terminals. */
  public static int number() {return _all.size();};

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
 
  /** Static counter to assign unique index. */
  protected static int next_index = 0;

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

  /** Special terminal for end of input. */
  public static final terminal EOF = new terminal("EOF");

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

  /** special terminal used for error recovery */
  public static final terminal error = new terminal("error");

  /*-----------------------------------------------------------*/
  /*--- General Methods ---------------------------------------*/
  /*-----------------------------------------------------------*/

  /** Report this symbol as not being a non-terminal. */
  public boolean is_non_term() 
    {
      return false;
    }

  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

  /** Convert to a string. */
  public String toString()
    {
      return super.toString() + "[" + index() + "]";
    }

  /*-----------------------------------------------------------*/

};